It is conventional practice in the prior art relating to directional valves to provide a mounting surface on one side of the valve body and to secure to that side a terminal block containing a ground connector and electrical connectors to which electrical leads from each solenoid extend and are connected. A junction box is releasably mounted on the mounting surface so as to enclose the terminal block, and the junction box is provided at one end with an electrical conduit port for receiving or mounting a receptacle through which electrical current from an external source can be supplied to the terminal block for actuating the one or two solenoids of the directional valve. In this respect, it is known to mount an electrical conduit receptacle in the electrical conduit port of the junction box and to provide suitable leads that extend from the receptacle to the terminal block. The electrical conduit may have at its end either a five pin plug (for double solenoid valves) or a three pin plug (for single solenoid valves) by which it is connected to the receptacle. It is also known to extend the individual conductors from the receptacle to an electrical plug that is structurally separate from the junction box but located therein, and to plug this electrical plug onto the terminal block to complete the required electrical circuits associated with the solenoids. In these prior art structures the terminal blocks are constructed and arranged so that the connectors will be located adjacent to their associated solenoids.
It is desirable when using directional valves of the foregoing character to provide indicators for revealing to operators when a solenoid of the valve is energized. For this purpose, the prior art discloses the use of light indicator means. A construction of this type is normally provided by connecting a lamp socket into the circuit of each solenoid so that when the solenoid is energized, a lamp in the socket will be illuminated. By locating the lamp adjacent to the solenoid, the operator can readily identify the solenoid that is energized.
Because of the confined working space and large number of electrical leads that must be connected to the terminal block, to the electrical plug and to the other components, substantial labor costs are involved in original equipment manufacture as well as in an installation at the site of use of the directional valve, and subsequently, also for maintenance purposes. Further, the possibility that erroneous connections can be made is significant.
Particular problems may also arise in some instances during installation or maintenance. During assembly of the original equipment, the electrical apparatus must be connected together without knowledge of the direction from which the source of electric power will be supplied and without knowledge of mounting restrictions that may exist for the directional valve. Often at the site of installation it becomes necessary to reverse the longitudinal direction of the junction box with respect to the valve body so that the electrical conduit port and the receptacle face the opposite direction from that of a conventional mounting. To provide continuity of operation of the solenoids, the ground connectors and the indicator lamps then involves substantial rewiring at the site when using prior art structures.
The problems of maintaining continuity of operation is equally great when the electrical apparatus includes an electrical plug that is plugged onto the terminal block, because prior art structures have their connectors oriented so that the plug cannot be rotated one hundred eighty degrees and then be replugged into the terminal block.
Still additional problems exist in relation to the prior art structures when rewiring is necessitated in those directional valves which have lamps to indicate when and which solenoid is energized. Code restrictions in many parts of the country limit the number of leads that can be connected to a connector of the terminal block, necessitating splicing the electrical leads from the lamp into the leads from the solenoid. In the prior art structures, these spliced connections must be disconnected and new splicings made if the junction box is to be reversed in its mounting on the valve body. Not only is a significant labor cost involved in making a change of this character, but the likelihood of making an improper connection is significant.
Thus, the prior art structures in this field leave much to be desired, because unduly complex wiring is involved for operating the directional valves, and the connections must be made in relatively confined spaces creating substantial labor problems. This is especially true during installation of the directional valves at a local site where the original wiring to the terminal blocks must be changed to accommodate local mounting requirements. To overcome these problems, there is a need for improved terminal block apparatus which can be assembled more easily and quickly, and which when assembled, will allow the reversal of the position of the electrical plug and junction box while providing electrical circuits that have continuity of operation relative to grounding, solenoids and indicator lamps.